Aromatic iron carbonyls



United States Patent 3,073,855 AROMATIC HRGN CARBONYLS Robert J. Harper, Baton Rouge, 1a., assignor toEtliyl Corporation, New York, N.Y., a corporation of Dela ware No Drawing. Filed Dec. 23, 19%, Ser. No. 77,844 4- Claims. (6%. 260-439) This invention relates to certain aromatic iron carbonyl compounds and more particularly to aromatic iron carbonyl compounds where the aromatic hydrocarbon is a condensed (i.e., fused) ring hydrocarbon.

Up to this time there have been several aromatic metal carbonyl compounds produced, none of which however have been iron compounds. One such prior compound is benzene chromium tricarbonyl in which there is chemical bonding involving all 6 aromatic carbon atoms of the resonating system. Another prior compound is dibenzene chromium which also has a rare gas structure in which each aromatic ring contributes 6 electrons to the metallic atom. Veltman, in US. Patent 2,409,167, describes producing an iron carbonyl compound which is bonded to an unsaturated hydrocarbon such as butadiene at a temperature of between 100300 F. in liquid phase at elevated pressures to obtain a compound such as butadiene iron tricarbonyl. Many attempts have been made to attach iron to an aromatic hydrocarbon ring, all of which have ended in failure. Surprisingly enough, this invention relates to the successful production of certain aromatic iron carbonyl compounds.

Accordingly, it is an object of this invention to produce aromatic iron carbonyl compounds. Another object is to provide a new class of compounds for use as antiknock agents in gasoline. Other objects of this invention will be obvious from the discussion which follows.

It has now been found that these and other objects are accomplished by the provision of fused ring aromatic iron tricarbonyl compounds. More particularly, these compounds have the formula ArFe(CO) wherein Ar is an aromatic condensed ring hydrocarbon containing up to about 20 carbon atoms. A preferred embodiment of this invention is naphthalene iron tricarbonyl and alkyl-substituted naphthalene iron tricarbonyls, while the most preferred embodiment is anthracene iron tricarbonyl and alkyl-substituted anthracene iron tricarbonyls. These compounds are preferred because of their simplicity of preparation and because of the availability of raw materials for their preparation.

The preferred aromatic hydrocarbons are aromatic condensed ring hydrocarbons such as anthracene, naphthalene and naphthacene which can be substituted with one or more alkyl groups, e.g., 1,4-dimethylnaphthalene,2,4-dimethylanthracene, etc. However, aromatic condensed ring hydrocarbons containing other substituents may be utilized. Examples of the substituted aromatic condensed ring hydrocarbons which may be used are 2-bromonaphthalene, l-chloronaphthalene, 2-chloronaphthalene, 1,7- dichloronaphthalene, 1,8-dinitronaphthalene, l-phenylnaphthalene, 2,4-dichloroanthracene, 2-chloroanthracene, and the like. Thus, in addition to or in lieu of alkyl substituents, the fused ring hydrocarbons can be substituted with halo groups (preferably chlorine, bromine, or both), nitro groups, aryl groups, and the like.

Examples of the compounds of this invention are2- bromonaphthalene iron tricarbonyl, l-chloronaphthalene iron tricarbonyl, 2-chloronaphthalene iron tricarbonyl, 1,7-dichloronaphthalene iron tricarbonyl, 1,4-dimethylnaphthalene iron tricarbonyl, l-phenylnaphthalene iron tricarbonyl, 2,4-dimethylanthracene iron tricarbonyl, naphthacene iron tricarbonyl, and the like.

Patented Janis, 1,953

2 The bonding of the metal to the aromatic ring structure forms a unique part of this invention. The conversion of the aromatic compound to the complex, aromatic metal carbonyl, results in only 1 ring of said aromatic compound being affected, and this donates only4 electrons to the metal. A most amazing feature of this invention is the fact that the aromatic rings partake of partial aromatic bonding with iron. This is the first time that iron has ever successfully been bonded to a fully aromatic hydrocarbon and, so far as isknown, the first instance where only two of the double bonds of an aromatic group have been shown to coordinate with a metallic atom.

Thus, Without desiring to be bound by theoretical considerations, the chemical evidence indicates that the bonding is similar to that of the following formula where the iron is coordinated with a portion of only one ring of the aromatic hydrocarbon (aromatic ring No. 1) which donates the four electrons. In all other known cases where aromatic groups are bonded to metals, the bonding is either sigma bonded in which a proton has been removed from the aromatic moiety or all three double bonds in the ring partake in bonding to the metal.

The compounds of this invention are best prepared by reacting iron dodecacarbonyl [Fe(CO) with the appropriate condensed ring hydrocarbon in an inert solvent. It is highly desirable to carry out this process under an inert atmosphere such as dry nitrogen, argon, neon, krypton, gaseous parafiinic hydrocarbons or the like. A unique feature of this invention is that in the above reactions iron dodecacarbonyl ([Fe(CO) gives infinitely better results than does iron pentacarbonyl (Fe(CO) The following examples illustrate the preparation of the compounds of this invention. In these examples all parts are given in parts by weight.

EXAMPLE I EXAMPLE II Into a flask were introduced 5.04 parts of iron dodecacarbonyl, 5.34 parts anthracene and 51 parts benzene. The reaction was flushed with nitrogen and heat was applied. After a 2.5 hour period, 2.3 parts ethanol were added. The reaction was refluxed for 20 hours. The reaction mixture was then filtered in a dry box. Then, the solution was filtered through alumina to yield a pale orange colored solution. This solution was evaporated to dryness to yield orange colored anthracene iron tricarbonyl crystals. These undergo decomposition at 0., show strong bonds in the infrared at 4.85, 5.01 and 5.13 microns. Calcd. for anthracene iron tricarbonyl,

Found: Fe=l8.4, C=63.83, H=3.6.

In sharp contrast to the foregoing results, mononuclear aromatic hydrocarbons will not produce organometallic products when reacted with iron carbonyl. By way of example, when the procedure described above involved 3 mesitylene in lieu of anthracene no products were obtained.

Comparative Example Iron dodecacarbonyl (15 parts) was mixed with 90 parts of mesitylene. The reaction was flushed with nitrogen and heat was applied to the reflux temperature of the system for a period of 8 hours. The mixture was filtered but no mesitylene iron carbonyl compound was obtained.

The reactions used to make the compounds of this invention may be conducted at a temperature of from about 50 C. to about 200 C., since in general these are the temperatures sufiicient to effect the desired reaction. The preferred temperatures are from about 80 C. to about 110 0., especially when an inert solvent is employed. The solvents particularly suitable for this invention are aliphatic, cycloaliphatic and aromatic hydrocarbons, although ethers and chlorinated hydrocarbons can be used.

Typical examples of suitable solvents for the present invention are decane, cyclohexane, benzene, toluene, xylene, mesitylene, ethylbenzene, diethylbenzene, trichlorobenzene, tetrahydrofuran, ethylene glycol dimethylether, ethylene glycol diethylether, diethylene glycol dimethylether, diethylene glycol dibutylether, diethylene glycol methylethylether, and the like.

The reaction time can vary, depending upon the amounts of reactants used and the solvents employed. Generally reaction times from about 30 minutes to about 30 hours will be sufiicient. The preferred reaction time is usually from about 3 hours to 15 hours.

The compounds of this invention have utility as additives to fuels having a boiling point range of gasoline for use in internal spark ignition engines as antiknocks. The gasoline may be clear (i.e., unleaded) or it may contain an alkyllead antiknock agent, such as tetraethyllead, tetramethyllead, and the like. In either event, concentrations of one or more of the compounds of this invention ranging from about 0.005 to about 2 grams of iron per gallon of the fuel give excellent results, especially in increasing the octane quality of the fuel. The present compounds also serve as lubricity improvers when used in natural or synthetic lubricating oils. These compounds may also be used as intermediates in the preparation of other organic compounds and as catalysts in the polymerization of alpha olefins, such as ethylene, propylene, butene-l, 3- methylbutene'l, 4-methylpentene-l, and the like. In this last-named use, the novel iron compounds are preferably employed in approximately stoichiometric proportions with an organo alkali, organo zinc or organo aluminum compound, e.g., butyl lithium, ethyl sodium, methyl potassium, diethyl zinc, triethyl aluminum, triisobutyl aluminum, diethyl aluminum hydride, ethyl aluminum sesquichloride, etc. The compounds of this invention may also be used in agricultural chemicals, e.g., as fungicides, herbicides and pesticides.

While this invention has been described with particular reference to iron compounds, it will be understood that the principles of operation as herein described can be applied with equal success to the corresponding compounds of ruthenium and osmium. Thus, it will be understood that this invention may be applied to the provision of such compounds as naphthalene ruthenium tricarbonyl, anthracene ruthenium tricarbonyl, naphthalene osmium tricarbonyl, anthracene osmium tricarbonyl, naphthacene osmium tricarbonyl, and the like, the synthesis of which will now be apparent to those skilled in the art.

Having thus described the compounds of this invention and methods for preparing the same, it is not intended that this invention be limited except as set forth in the following claims.

What is claimed is:

1. An aromatic iron carbonyl compound having the formula ArFe(CO) wherein Ar is an aromatic condensed ring hydrocarbon containing up to about 20 carbon atoms.

2. Naphthalene iron tricarbonyl.

3. Anthracene iron tricarbonyl.

4. The method of producing aromatic iron carbonyls comprising reacting iron dodecacarbonyl with an aromatic condensed ring hydrocarbon containing up to about 20 carbon atoms in an inert solvent at a temperature sufficient to elfect said reaction.

References Cited in the file of this patent UNITED STATES PATENTS 2,409,167 Veltman Oct. 8, 1946 

1. AN AROMATIC IRON CARBONYL COMPOUND HAVING THE FORMULA 